I have a Droid 2. IMHO, I don't think the phone is rugged enough to withstand the shock it would receive from mounting it on the stem or handlebars. I put my phone in a plastic bag in the pocket of my jersey.

RAM Mounts. In particular, look at the "RAM Mount Cradle Plate EZ-Strap Bike Mount RAP-SB-187U" and the "RAM Mount Cradle Plate Handlebar Bike Mount RAP-274-1U". I use them to mount a handheld VHF/UHF "ham" radio. You'd have to look for a case that can hold the Droid and attach to the mount. For the radio, I use their "RAM Mount Plastic Universal Belt Clip Bar Cradle Holder RAM-HOL-BC1U". You could possibly install the Droid in a Otterbox or similar case and rig a belt clip to hook into the holder.

The mounts are not perfect - the stap mount was tricky to install; I replaced the factory pin (could never get it to click in) with a longer, similar diameter steel rod and snipped off the excess. The mount has a slight tendency to rotate forward (the radio I use sits a little top-heavy). It supports the radio well, and is easily moved from one bike to another. A phone is lighter and the weight distribution is more even so I think it would stay put better. I've used this mount on several 50 mile rides and have been trying it out for about a week on a 12 mile-each way commute.

The 274-1U mount can be put on handlebars or the stem (I have it that way on 1 bike) which eliminates any fore-aft tipping. Like some other reviewers, I've broken off a pin in the pin connector (maybe this is why RAM sells the RAP-274-1B3 as a replacement part) - the problem seems to be movement between the plastic housing of the mount and a rubber insert that adheres to the stem or handlebar. Moving the mount between bikes requires cutting zip-ties; I bought a bag from the big box hardware store (needed them anyway) and got a 2nd mount for the other bike. Wihout the cradle and radio, it looks small and unobtrusive, like a mount for a bike computer. I've used this mount on several full century rides and the radio has stayed rock-solid. If you want a more permanent-looking mount, get one of the models RAM sells for motorcycles - they use a U-bolt and won't come loose without tools.

There will be vibration and you will not want to use a very rigid mount - both these mounts have some limited degree of movement which helps dampen vibrations. But, if you are going to use headphones, stick the phone in something to keep moisture off it and use an armband or put it in a jersey pocket - no wires then between you and the bike. If you are using the phone as a GPS/map display or bike computer, it'll work but expect to kill the battery faster. Ask yourself if using a several hundred dollar phone is better than a cheaper music player, bike computer, or GPS designed for that environment. I'd put the phone in a water-resistant case for protection; I've found that the Droid and HTC Incredible are both very senesitive to moisture (sweat, even light rain, water bottle spills) and need some protection. Assume the D2 is not any better.

I use a bag from Velotrac for my Android (original Mot. Droid), and it works fine. Agree with Steve530 that the phone is not rugged enough for me to feel comfortable with it being mounted like a normal cycle computer, where it is exposed to vibration, rain etc.

The bag sits on my top tube, and allows you to see and control the phone through the transparant plastic window.

I got mine for my Droid 1 at amzer.com might want to check out google and amazon to. Try to find one specifically made for your phone as it will be more secure than a universal. Ive put over 6000 miles on with my phone mounted and have no issues. Only thing i really do special is wrap my headphones around my mount twice so in case i do something stupid like whip head back to far i dont rip it off the mount. One other suggestion is spending 5 bucks on an extra battery. When i do day long rides it comes in handy when gps tracking, listening to music and checking maps all day.

I have the same Amzer mount and use it all the time with my Droid 2; HOWEVER, people here need to know something important about this mount. The mount is in two pieces and one slides into the other and is supposed to lock. Under hard use, the mount can separate and your phone will go flying.

I had it happen to my phone going over some railroad tracks at 25mph. The phone FLEW down the road and fortunately chipped up small portions of the bevel but didn't scratch the face.

To fix it and ensure it doesn't happen again, I got some polystyrene glue to weld the plastic pieces together. Now it seems completely stable.

I have the same Amzer mount and use it all the time with my Droid 2; HOWEVER, people here need to know something important about this mount. The mount is in two pieces and one slides into the other and is supposed to lock. Under hard use, the mount can separate and your phone will go flying.

I had it happen to my phone going over some railroad tracks at 25mph. The phone FLEW down the road and fortunately chipped up small portions of the bevel but didn't scratch the face.

To fix it and ensure it doesn't happen again, I got some polystyrene glue to weld the plastic pieces together. Now it seems completely stable.

I have never had my phone come off this mount because of road conditions, the mount snaps into the base very securely. I did have my phone get ripped off the mount once when i first owned it when i pulled my head back quickly out of range, causing my headphone wire to rip it out of the mount. (the droid 1 earphone jack is very tight, but this is a good thing) But as i mentioned in my previous post that is why i now wrap my headphones around the mount base twice, then in a worst case scenario my earbuds come out but my phone stays securely on the mount. I have actually gone thru a few pairs of earbuds due to this because the wires got caught in my wheel after they were pulled out of my ears, but id rather replace a 30$ pair of earbuds than my phone.